Recently, as it has become necessary to reduce the weight of automobiles, and the use of large and complex electrical and electronic devices has increased, there has appeared a need to develop thermoplastic resins having the requisite physical properties, such as heat resistance and impact resistance. In particular, in applications such as automobile interior materials, and information technology components such the cases of computers and other electronic devices, there is a preference for matte or low-gloss properties, not only for reasons of external appearance, but also to enable the elimination of expensive coating or painting operations. Moreover, recently, there has been increased interest in environmentally friendly materials. Accordingly, the need for developing materials that meet such needs has increased.
Typically, propylene resins are widely used as automobile interior materials. Such propylene resins are known for being less glossy than some thermoplastic resins. However, such propylene resins are deficient in terms of properties such as rigidity and scratch resistance. Although methods have been proposed for adding fillers and other additives to make up for such deficient properties, such properties are still deficient and thus limit the use of the propylene materials as automobile interior materials.
Moreover, resins, such as high impact polystyrene resins prepared by mixing polybutadiene and polystyrene, which exhibit matteness due to the addition a matting agent have been developed. However, as in the case of the propylene resins, there is a limitation in that a balance between the properties, such as matteness, heat resistance, and impact resistance, required by automobile interior materials is not achieved.
Meanwhile, acrylonitrile-butadiene-styrene (hereinafter, ABS) resins, methylmethacrylate-butadiene-styrene (hereinafter, MBS) resins, acrylate-styrene-acrylonitrile (hereinafter, ASA) resins, acrylic impact modifier (AIM) resins, and the like prepared through emulsion polymerization are excellent in terms of physical properties such as impact resistance, rigidity, and flowability and the like, and thus are widely used as modifiers for various plastics.
In particular, the ABS resins have excellent dimensional stability, processability, and chemical resistance, and thus are widely used as materials of monitor housings, game console housings, home appliances, office equipment, and automobile lamp housings and the like. Recently, much research is being carried out on using such ABS resins, having excellent impact resistance, chemical resistance, and processability, as automobile interior materials by imparting the ABS resins with heat resistance and matteness.
For example, a method for improving such ABS resins by preparing the ABS resins as rubber particles having large diameters of at least 1 μm has been proposed, but resins prepared using the method have an insignificant matteness effect, and have limitations of poor impact strength and heat resistance. Another method for improving such ABS resins by inserting matter fillers having a particle size of at least 5 μm has been proposed, but the prepared resins, while exhibiting excellent processability, are insufficiently matte, and have a limitation in that degradation of the impact strength is particularly severe. Moreover, a matte filler is added to impart matteness, but since a large amount is required for matteness to be imparted, impact strength is consequently degraded, and there limitations such as increased production cost.
In addition, the ABS resin prepared through emulsion polymerization has a high content of volatile organic compounds (VOC), and thus has a limitation of being difficult to adopt as an environmentally friendly material.
Meanwhile, recently, the use of ABS resins, which are prepared through bulk polymerization, bulk-solution polymerization, or bulk-suspension polymerization by using maleimide compounds as additional monomers, as materials requiring heat resistance and matteness has been proposed.
For example, U.S. Pat. No. 4,808,661 discloses an ABS resin composition prepared through a continuous bulk polymerization method in which a maleimide compound is introduced over several different points in time during a polymerization process. U.S. Pat. No. 5,091,470 indicates that an ABS resin having excellent heat resistance, impact resistance, and matteness may be prepared by introducing a maleimide compound over several different points in time during a polymerization process such that a portion is introduced after phase inversion has occurred. Moreover, U.S. Pat. No. 5,412,036 indicates that an ABS resin having increased impact resistance may be prepared through a continuous bulk polymerization method in which a maleimide compound is introduced over several different points in time, wherein the conversion rate is different at each point in time. However, such methods have the inconvenience of requiring a maleimide compound to be introduced over several different points in time, and introducing the maleimide compound over several different points in time may cause the stability of the maleimide compound in the reactor to degrade such that the maleimide compound is phase separated from other components. Moreover, there is a limitation in which the size of rubber particles formed in the ultimately prepared ABS resin is non-uniform.
Therefore, there is a need for developing a resin having matteness, excellent mechanical/chemical properties, such as impact resistance and heat resistance, and also having a low content of volatile oraganic compounds.